Echinacea for preventing and treating the common cold

Preparations of the plant Echinacea (familiy Compositae) are widely used in some European countries and in North America for common colds. Most consumers and physicians are not aware that products available under the term Echinacea differ appreciably in their composition, mainly due to the use of variable plant material, extraction methods and addition of other components. Now we assessed whether there is evidence that Echinacea preparations are 1) more effective than no treatment; 2) more effective than placebo; 3) similarly effective to other treatments in A) the prevention and B) the treatment of the common cold. Outcomes of interest in prevention trials were: number of individuals with one or more colds, and severity and duration of colds; and in treatment trials: total symptom scores, nasal symptoms and duration of colds. Sixteen trials including a total of 22 comparisons of an Echinacea preparation and a control group met the inclusion criteria. The majority had reasonable to good methodological quality. A variety of different Echinacea preparations were used. None of the three comparisons in the prevention trials showed an effect over placebo. Comparing an Echinacea preparation with placebo as treatment, a significant effect was reported in nine comparisons, a trend in one, and no difference in six. More than one trial was available only for preparations based on the aerial parts from Echinacea purpurea. Therefore we concluded that preparations based on aerial parts of E. purpurea might be effective for the early treatment of colds in adults but results are not fully consistent. Beneficial effects of other Echinacea preparations and for preventative purposes might exist but have not been shown in independently replicated, rigorous randomized trials. [1,2] Again a recent meta-analysis reported that standardized extracts of Echinacea were effective in the prevention of symptoms of the common cold after clinical inoculation, compared with placebo. [3]

References: [1] Linde K., Barrett B. et al. (2006) The Cochrane Database of Systematic Reviews Issue 1. [2] Gillespie E.L., Coleman C.I. (2006) Conn. Med. 70: 93–97. [3] Schoop R., Klein P. et al. (2006) Clin. Ther. 28: 174–183.